Sweep transformer



June 13, 1961 z s r 2,988,715

SWEEP TRANSFORMER Filed Sept. 2, 1958 Il/III//// M/VENTOR ATTORNEY United States Patent 2,988,715 SWEEP TRANSFORMER Leo A. Gizynski, Riverside, and Richard 0. Gray, Broadview, 111., assignors to Zenith Radio Corporation, a corporation of Delaware Filed Sept. 2, 1958, Ser. No. 758,497 8 Claims. (Cl. 336-96) then applied to the final anode electrode of the cathoderay tube. Since final anode voltages utilized in current picture tubes are of the order of 20,000 volts, the induced voltage appearing across the high potential coil is substantial. While conductors having adequate insulating properties are readily available for such circuits, the formation of corona, a gaseous discharge attributable to the ionization of the air adjacent a surface which supports a high potential electric field, presents a significant problem. Corona, in addition to producing an objectionable odor, deteriorates insulating material thus aggravating the problem of insulating high voltages. An obvious deterrent to the formation of corona is to insulate the coil turns and particularly to coat with an insulating material any exposed conductive surfaces, such as the coil terminals, which support a high potential thus avoiding an air dielectric adjacent such surfaces.

In accordance with present practices, the avoidance of corona discharge from high potential coils entails a number of costly and time consuming operations. Specifically, after the winding operation is completed, the coil is impregnated and then coated with an insulating compound. Thereafter the coil is positioned upon a coil form having terminal lugs which secure break-out leads from the coil winding and also provide a connection for external circuitry. Since the coil is to be mounted upon the transformer core, an inner lining of insulating material must be positioned between the core and the terminal supporting coil form to insulate the terminals from the core. Alternatively, the inner liner may be discarded and an elongated coil form utilized to position the coil terminals beyond the core. In either instance after connection to the associated circuitry has been effected, the exposed high-potential terminals must be coated with an insulating compound to avoid an air dielectric adjacent the high-potential surfaces. These prior art units are thus characterized by a rather expensive construction and less than satisfactory corona preventing provisions.

It is therefore an object of the invention to provide a coil housing for supporting an electrical coil within a substantially completely enveloping insulating compound.

It is also an object of the invention to provide a coil housing which permits a complete enveloping of an electrical coil and its terminals to prevent the formation of corona.

It is another object of the invention to provide a coil housing which provides an improved insulation for the coil while obviating the costly construction of prior art units.

It is also an object of the invention to provide a coil housing which insulatingly supports an electrical coil and further serves as a mold for the insulating compound.

A coil housing for supporting an electrical coil having at least one high-potential terminal Within a substantially completely enveloping insulating compound comprises a Patented June 13, 1961 hollow post for receiving the coil as a core. The post has a maximum cross-sectional dimension approximately equal to the internal diameter of the coil and a configura tion such as to engage the inner periphery of the coil at spaced points. The length of the hollow post exceeds that of the coil. The post is affixed to a transverse end wall while a shell, likewise afiixed to and projecting from the end wall, surrounds the post. The internal dimension of the shell exceeds the external diameter of the coil and has a length exceeding that of the coil so as to define with the post and the end wall a chamber for receiving, supporting, and positioning the coil in such a manner that an insulating compound introduced into the chamber substantially completely encloses the coil to prevent the formation of corona. In a particular embodiment of the invention, a portion of the shell is deformed to constitute a recess for receiving the high-potential terminal of the coil when the coil is positioned in the chamber.

While the invention is especially applicable to a housing for supporting a single electrical coil, it likewise contemplates a structure for supporting more than one coil. Specifically, such a coil housing includes a pair of hollow posts which individually support respective ones of the coils. In all other respects this coil housing is substantially similar to the single post housing.

The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be understood, however, by reference to the following description taken in conjunction with the accompanying drawing, in the several figures of which like reference numerals identify like elements, and in which:

FIGURE 1 is an elevation view, partly in section, of a sweep transformer employing a coil housing constructed in accordance with the invention;

FIGURE 2 is an exploded view illustrating structural features of the housing;

FIGURE 3 is a sectional view of the flange portion of the coil housing taken along line 3-3 of FIGURE 1;

FIGURE 4 is a fragmentary sectional view of the coil housing of FIGURE 1 showing an alternative center post construction;

FIGURE 5 is a cross-sectional view of the taken along line 2-2 of FIGURE 1; and

FIGURE 6 shows a sweep transformer employing a coil housing which comprises an alternate embodiment of the invention.

The sweep transformer 10 shown in FIGURE 1 comprises a pair of C-shaped core members 11, 12 positioned in an abutting relation to define a pair of transverse core legs 13, 14 to form a continuous magnetic core. The magnetic core is secured to a base 15 by a U-shaped strap 16. A primary winding 17 having an output terminal 18 is disposed upon an elongated form 19 and mounted upon core leg 13. Form 19 is provided with the terminal legs 20 which are individually connected to taps on winding 17. An inner-liner 21 is disposed between form 19 and core leg 13 to insulate terminals 20 from the core leg. The construction of coil 17 as well as its mounting provisions are typical of the prior art construction previously adverted to.

In accordance with the invention a coil housing 25 for supporting a high potential coil 26 is mounted upon core leg 14. Coil 26 has predetermined internal and external diameters and includes a low-potential input terminal 27 which is connected to terminal 18 of winding 17 by the conductor 28 and a high-potential output terminal 29 terminated by a conductor 30 and a cap 31 for connecting coil 26 to a high voltage rectifier, not shown. The coil is incapsulated within a substantially completely envelopcoil housing 'ing insulating compound 32. Coil housing 25, best shown.-

in FIGURE 2, is constructed of an insulating material such as alkyd and comprises a hollow center post 33 for receiving coil 26 as a core. Post 33 has a maximum crosssectional dimension approximately equal to the internal diameter of coil 26 and a length exceeding that of the coil. The external wall of post 33 is so configurated as to engage the inner periphery of coil 26 at spaced points, specifically post 33 includes a plurality of lands 34 which engage the inner periphery of coil 26 and define a series of interstices 35. Post 33 is aflixed to a transverse end wall 36 having spacer means, more particularly, a plurality of pedestals 37 projecting from the end wall, for spacing coil 26 from end wall 36. A shell 38 is likewise affixed to end wall 36 and projects therefrom to surround post 33. The minimum internal dimension of shell 38 exceeds the external dimension of coil 26 while the length of shell 38 exceeds that of the coil. Post 33 in conjunction with end wall 36 and shell 38 define a chamber for receiving, supporting, and positioning coil 26 within the insulating compound 32. A portion 39 of shell 38 is deformed to constitute a recess for receiving high-potential terminal 29 when coil 26 is positioned within housing 25. The inner periphery of post 33 is coated with a conductive material such as aquadag, indicated by reference numeral 42, which is conductively connected to core leg 14 by strap 16. Conductive coating 42, in effect, eliminates an air dielectric between post 33 and the core thus obviating corona discharge in this area.

Center post 33 further includes provisions for indexing the post upon core leg 14. Specifically, the post is provided with a depending flange 40, having a slotted portion 41, best shown in FIGURE 3, for engaging core member 12 to orient housing 25 upon the core.

FIGURE 4 discloses an alternative construction of center post 33 wherein tapered lands 34', only one shown, are utilized for supporting coil 26. In this construction the spacer pedestals can be dispensed with since the tapered lands in addition to insuring adequate clearance between end wall 36 and coil 26 also support the coil.

FIGURE 5 illustrates more clearly how coil 26 and the high-potential terminal 29 are received within housing 25 and the construction of housing 25 whichpermits insulating compound 32 to fill interstices 35 so as to completely enclose coil 26 and its terminals.

In assembling coil housing 25, the high-potential coil 26 is first impregnated with varnish and thereafter has conductors 28 and 30 secured to terminals 27 and 29 respectively. The coil is then positioned upon post 33 with high-potential terminal 29 received within the recess defined by deformed portion 39 of shell 38. Thereafter a quantity of insulating compound 32, which in a preferred embodiment of the invention comprises a thermosetting polyester, is introduced into housing 25in a viscous state. The housing itself serves as a mold for this material. A sufficient quantity of compound is utilized so that substantially all the undisplaced volume of housing 25 is occupied. As shown in FIGURE 5, the compound fills interstices 35 to envelope high-potential coil 26 and its terminal connections. The compound upon solidifying completely encloses coil 26 and its terminals thus precluding an air dielectric adjacent surfaces of coil 26 which support high electric potentials.

The advantages of a coil assembly employing the invention are obvious when the incapsulation of coil 26 is compared to prior-art practices as evidenced by the construction of coil 17. For example, coil form 19 and the innerliner 21 as well as an input terminal lug are dispensed with. Furthermore, housing 25 in serving as a mold for insulating compound 32 enables the high-potential coil as well as its terminals to be completely enclosed within the insulating compound.

While it is recognized that it is primarily the highpotential coil 26 of a sweep transformer which is most susceptible to corona discharge, the teachings of the invention contemplate the use of a coil housing for supportingrnor'e than one coil. In FIGURE 6, a coil housing 2.5 for supporting a pair of electric coils is shown. In substance, housing 25' comprises a pair of substantially similar hollow center posts 33 for individually supporting coils 17 and 26. The posts are aflixed to a transverse end wall 36' while the shell 33 aflixed to end wall 36' surrounds posts 33. The inner peripheries of posts 33 are coated with an aquadag 42' to eliminate an air dielectric in these regions. The minimum internal dimension of shell 38' where it parallels a coil exceeds the external dimension of that coil while the length of the shell exceeds that of either coil. The posts in conjunction with end wall 36' and shell 38' define a kidney-shaped chamber for receiving, supporting, and positioning coils 17, 26 within the insulating compound 32. Since housing 25' is mounted upon oppositely disposed core legs indexing provisions are unnecessary.

In using a sweep transformer employing housing 25' additional benefits obtain in that coil form 19 and its terminals 2% may be dispensed with. The external leads are connected to various coil connections prior to positioning the coils within the housing as shown in FIGURE 2. The subsequent potting operation envelops each coil and its terminal connections within insulating compound thus insuring protection against corona discharge while providing secure electrical connections to the coils.

The invention in providing a novel housing for receiving and supporting an'electrical coil within an insulating compound, avoids the limitations of the prior art and further effects a significant savings in the cost of manufacturing potted high potential coils.

While particular embodiments of the present invention have been shown and described, it is apparent that changes and modifications may be made therein without departing from the invention in its broader aspects. The aim of the appended claims, therefore, is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

We claim:

1. A coil housing for supporting an electrical coil having predetermined internal and external diameters within a substantially completely enveloping insulating compound, said housing comprising: a hollow post for receiving said coil as a core, having a maximum crosssectional dimension approximately equal to the internal diameter of said coil, having such configuration as to engage the inner periphery of said coil at spaced points thereof, and having a length exceeding that of said coil; a transverse end wall to which said post is affixed; and a shell affixed to and projecting from said 'end wall and surrounding said post, having a minimum internal dimension exceeding the external diameter of said coil, having a length exceeding that of said coil and defining with said post and end wall a chamber for receiving, supporting, and positioning said coil such that an insulating compound introduced into said chamber substantially completely encloses said coil to'prevent the formation of'corona.

2. A coil housing for supporting upon a magnetic core an electrical coil having predetermined internal and external diameters immersed within a substantially completely enveloping insulating compound, said housing comprising: a hollow post having such configuration as to engage the inner periphery of said coil at spaced points thereof forrec'eiving said-coil as a core, having a length exceeding that of said coil, and having provisions for indexing said post upon said magnetic core; a coating of conductive material disposedupon the inner surface of said hollow post and conductively engaging said core for eliminating an air dielectric between said post and said core; a transverse end wall to which said post is aflixed; and a shell affixed to and projecting from said end wall and surrounding said post, having a'minimurn internal dimension exceeding the external diameter of saidco'il, having a length exceeding that of said coil and defining with said post and end wall a chamber for receiving, supporting, and positioning said coil such that an insulating compound introduced into said chamber substantially completely encloses said coil to prevent the formation of corona.

3. A coil housing of an insulating material for supporting an electrical coil having predetermined internal and external diameters within a substantially completely enveloping insulating compound, said housing comprising: a hollow post having a plurality of lands for engaging the inner periphery of said coil at spaced points thereof for supporting said coil as a core, and having a length exceeding that of said coil; a transverse end wall to which said post is affixed; and a shell afiixed to and projecting from said end wall and surrounding said post, having a minimum internal dimension exceeding the external dimension of said coil, having a length exceeding that of said coil, and defining with said post and end wall a chamber for receiving, supporting, and positioning said coil such that an insulating compound introduced into said chamber substantially completely encloses said coil to prevent the formation of corona.

4. A coil housing for supporting an electrical coil having predetermined internal and external diameters within a substantially completely enveloping insulating compound, said housing comprising: a hollow post for supporting said coil as a core, having a maximum crosssectional dimension approximately equal to the internal diameter of said coil, having such configuration as to engage the inner periphery of said coil at spaced points thereof, and having a length exceeding that of said coil; a transverse end wall to which said post is aflixed; spacer means comprising a plurality of pedestals projecting from said end wall for spacing said coil from said end wall; and a shell aflixed to and projecting from said end wall and surrounding said post, having a minimum internal dimension exceeding the external diameter of said coil, having a length exceeding that of said coil and defining with said post and end wall a chamber for receiving, supporting, and positioning said coil such that an insulating compound introduced into said chamber substantially completely encloses said coil to prevent the formation of corona.

5. A coil housing for supporting upon a magnetic core an electrical coil having predetermined internal and external diameters immersed within a substantially completely enveloping insulating compound, said housing comprising: a hollow center post having such configuration as to engage the inner periphery of said coil at spaced points thereof for supporting said coil as a core, having a length exceeding that of said coil, and having provisions for indexing said post upon said magnetic core; a transverse end wall to which said post is centrally afiixed; and a shell aflixed to and projecting from said end wall and surrounding said post, having a minimum internal dimension exceeding the external diameter of said coil, having a length exceeding that of said coil and defining with said post and end Wall a chamber for receiving, supporting, and positioning said coil such that an insulating compound introduced into said chamber substantially completely encloses said coil to prevent the formation of corona.

6. A coil housing for supporting upon a magnetic core an electrical coil having predetermined internal and external diameters immersed within a substantially completely enveloping insulating compound, said housing comprising: a hollow center post having such configuration as to engage the inner periphery of said coil at spaced points thereof for supporting said coil as a core, having a length exceeding that of said coil, and including indexing means comprising a relieved flange depending from said post for orienting said post upon said magnetic core; a transverse end wall to which said post is centrally aifixed; and a shell afiixed to and projecting from said end wall and surrounding said post, having a minimum internal dimension exceeding the external diameter of said coil, having a length exceeding that of said coil and defining with said post and end wall a chamber for receiving, supporting, and positioning said coil such that an insulating compound introduced into said chamber substantially completely encloses said coil to prevent the formation of corona.

7. A coil housing for supporting an electrical coil having predetermined internal and external diameters, and having at least one high-potential terminal, within a substantially completely enveloping insulating compound, said housing comprising: a hollow post for supporting said coil as a core, having a maximum cross-sectional dimension approximately equal to the internal diameter of said coil, having such configuration as to engage the inner periphery of said coil at spaced points thereof, and having a length exceeding that of said coil; a transverse end wall to which said post is affixed; and a shell affixed to and projecting from said end wall and surrounding said post, having a minimum internal dimension exceeding the external diameter of said coil, having a length exceeding that of said coil, and defining with said post and end Wall a chamber for receiving, supporting, and positioning said coil, a portion'of said shell being deformed to constitute a recess for receiving said high-potential terminal when said coil is positioned within said hcusing, whereby an insulating compound introduced into said chamber substantially completely encloses said coil and said high-potential terminal to prevent the formation of corona.

8. A coil housing for supporting a pair of electrical coils having predetermined internal and external diameters Within a substantially completely enveloping insulating compound, said housing comprising: a pair of hollow posts for individually supporting respective ones of said coils as cores, having maximum cross-sectional dimensions approximately equal to the internal diameters of said respective coils, having such configuration as to engage the inner periphery of said respective coils at spaced points thereof, and having respective lengths exceeding that of said coils; a transverse end wall to which said posts are afiixed; and a shell affixed to and projecting from said end wall and surrounding said posts, having a minimum internal dimension parallel to said coils exceeding the external diameter of said coils, having a length exceeding that of said coils and defining with said posts and end wall a chamber for receiving, supporting, and positioning said coils such that an insulating compound introduced into said chamber substantially completely encloses said coils to prevent the formation of corona.

References Cited in the file of this patent UNITED STATES PATENTS 

